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[The Camry]

So two questions. 1. I understand that having a -12 slope gives you a 180 degree phase. Now I don't understand why flipping your speakers polarity/reversing phase digitally is required. Is the phase only flipped from where the x-over starts? Like say normal phase at 100hz then -12db lpf slope at 101hz. Does the 180 phase change only start at 101hz and up or does it effect the whole freq spectrum the driver plays. ie: 100hz and down as well as up.

2. If an amp has a -12 db crossover. Does it automatically flip its drivers polarity internally to keep them having a "normal" phase

and what happens when you have more than one crossover on a driver. like say its HP at 3k at -12 db and then HP again at 4k with..idk -6db. Does it become an -18 or how all does that work?

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[blazian87 10+ year member]

I never heard of a -12db slope automatically flipping the polarity of the driver. Where did you hear that from? and what is the logic behind it? From what I thought, reversing the polarity digitally is only done when you accidentally switch the + and - on the wire. Usually you pick whatever is louder, which is usually the normal phase. I guess depending on the application, sometimes reversing the phase can help the driver play a different way. It definitely sounds different, but I prefer to keep everything in phase. I also heard something about reversing the polarity on the sub so that it brings the sub stage closer up front, but I don't know how true that is.

Your second question though.. I don't think it's a good idea to put more than 1 crossover on a driver because it would interfere with each other. Like in your example HP 3k @ -12db and 4k @ -6db, I would assume it would act like a 4k @ -6db but with a sharper cutoff in the lower frequencies causing a slight dip in that area. But maybe you want to do this so you can still have your shallow -6db slope but without having the tweeter playing too low and damaging the tweeter I guess. That could be a possibility. I just don't think a -6db slope is a good place to start from because it tends to play too many frequencies at once, making it sound almost like a full range speaker with a little attenuation on the lower spectrum. It will not become a -18db slope combining them because -18db is much sharper than both of them so that's impossible. So if you can visualize how it looks on a graph, it'll look like a very shallow curve overall with a slight drop on the low end.

 

[hispls 5,000+ posts]

A DSP, amp, or store bought passive crossover network will give you in-phase outputs. Flipping output phase 180 degrees is something you only need to worry about when you're building your own crossovers.

Assuming you're trying to design your own passive crossover circuit, the phase is flipped for everything that comes through the circuit but the audible problems are generally only noticeable at the crossover points. That said, you're far more likely to run into phasing issues from speaker locations than anything else.

I'm not sure why you're trying to run multiple crossovers in the first place..... you're really trying to over-think this IMO>

 

[adulbrich 5,000+ posts]

I agree, you're over thinking things

 

[Seraphim38 10+ year member]

an offset of gain does not move the wave form 180 degrees forward or back. No, -12 dB does not equal a phasing adjustment.

It is true that phase can become problematic near crossover points, and it is most commonly prevalent in midrange voicing, and with lower frequencies, because the wave forms become progressively longer.

And yes, you can layer crossover signals by putting a 6dB slope crossover on top of a signal that already has a crossover slope in play. They are additive, but phasing can become complex. Simpler crossover networks are usually preferred.

 

[trumpet 5,000+ posts]

This discussion is a continuation of an existing thread started by the OP. http://www.caraudio.com/forums/general-discussion/619031-phase-bandpass.html